203 research outputs found
The Inverse Compton Thermostat in Hot Plasmas Near Accreting Black Holes
The hard X-ray spectra of accreting black holes systems are generally
well-fit by thermal Comptonization models with temperatures keV. We
demonstrate why, over many orders of magnitude in heating rate and seed photon
supply, hot plasmas radiate primarily by inverse Compton scattering, and find
equilibrium temperatures within a factor of a few of 100 keV. We also determine
quantitatively the (wide) bounds on heating rate and seed photon supply for
which this statement is true.
Plasmas in thermal balance in this regime obey two simple scaling laws, one
relating the product of temperature and optical depth to the ratio of seed
photon luminosity to plasma heating rate , the other relating the
spectral index of the output power-law to . Because is almost
independent of everything but , the observed power law index may be
used to estimate . In both AGN and stellar black holes, the mean value
estimated this way is . As a corollary, must
be -- 0.2, depending on plasma geometry.Comment: 26 pages, AASLaTeX, to appear in July 10 Ap.J. Figures available in
uuencoded form at ftp://jhufos.pha.jhu.edu/pub/put/jhk/comptfigs.u
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